At first glance, the Yelp document appears to be damning. After tracking the behavior of a bunch of web users who were overtly searching for restaurant reviews on Yelp, the survey produces a heatmap of what people actually click on once they get their search results. As Google inserts links to its own review products, like Google+ and Google Local, right under "natural" search results, many people who are searching for Yelp results actually end up on Google's pages, the document suggests.

But there are two underlying issues that complicate the document's apparent slam dunk against Google. The first is that Google does appear to have a conflict of interest between its search business and its newly prominent publishing business. The second is whether the fact that Google takes some clicks obscures the fact that Google is sending a majority of clicks to Yelp — clicks it would not have if Google didn't exist.

Here are the key slides from the confidential Yelp survey.

This slide shows how a user overtly searching for a Yelp review of the Gary Danko restaurant in San Francisco gets Google results ahead of Yelp results. Google shows the restaurant's official site first, as expected.

But under that it has attached "barnacle" links to Google content like Google Reviews and Google +:

Yelp

The Yelp survey shows that nearly 20% of clicks then end up on Google results, not Yelp results, even though the original search contained the term "Yelp":

Yelp

But Yelp's surveyors conclude that although 20% of clicks are siphoned by Google, Google "does NOT appear to have negatively impacted our overall traffic":

Here's an example. A search for Coca-Cola produces a giant display box for results featuring Google's own material:

Jim Edwards / BI

So although Google purports to offer the best search results, it also displays its own self-interested search results alongside and — as the Yelp survey makes clear — on top of natural search results.

But Sullivan notes that the clicks on Google results in the Yelp survey are mostly going to the restaurant's official site — a not unreasonable result. And only about 1.4% of clicks are being syphoned into Google Reviews, etc., Sullivan says.

In sum, that's one reason why Yelp's document both complains about Google's self-interested results while at the same time admitting that it has not hurt Yelp's traffic. And at a more basic level, there is the question of what Yelp's traffic would look like if Google didn't exist — because having 80% of people being able to find you easily isn't the worst thing in the world.